Combined cracking and coking broad oven of the recuperator type



Sept. 2, 1947. c. H; HUGHES I COMBINED CRACKING AND COKING BROAD OVEN OFTHE RECUPERATOR TYPE Filed June 1, 1945 6 SheetsSheet l IN VEN TOR.CHARLESKHHUG'HEE ATTORNEY P 1947- c. H. HUGHES 2,426,612

COMBINED CRACKING AND COKING BROAD OVEN OF THE RECUPERATOR TYPE FiledJune 1, 1945 6 Sheets-Sheet 2 Fig E.

INVENTOR. cwAkzesuuuqne-s ATTDQA/F p 1947- c. H. HUGHES 2,426,612

COMBINED CRACKING AND COKING BROAD OVEN OF THE RECUPERA'IOR TYPE FiledJune 1, 1945 6 Sheets-Sheet 3 ATTDRNEY p 2, 1947' I c. H. HUGHES2,426,612

CQHBINED CRACKING AND COKING BROAD OVEN OF THE RECUPERATOR TYPE FiledJune 1, 1945 6 Sheets-Sheet 5 I4mllgulzlllmualrluunulllzluzlu.rrmzlultgluulmw' lllmnlllllllllmlll m1 2 Fly]. 1

CfF 17-5 D16 10. 'INVENTOR.

DHARL EBJ-LHUGHES ATTDR'NEY Sept. 2, 1947. c. H. HUGHES COMBINEDCRACKING AND COKING BROAD OVEN OF THE RECUPERATOR TYPE 6 Sheets-Sheet 6Filed June 1, 1945 X kh Bk Wkb mkhxs 3.

.E H H .5 m5 1 VU K W MG mw Patented Sept. 2, 1947 COMBINED CRACKINGANDCOKING BROAD OVEN OF THE RECUPERATOR TYPE Charles H. Hughes, GlenRidge, N. J., assignor to Hughes By-Product Coke Oven Corporation, NewYork, N. Y., a corporation of \New York Application June 1, 1945, SerialNo. 597,028

(o1. fee-104) 13 Claims. 1

The present invention relates to a method of cracking or pyrolyticallytreating hydrocarbons to cause conversion thereof and to an improvedcracking and coking oven for carrying out the said method, and, moreparticularly, the invention relates to a method of pyrolyticallytreating in a broad cracking and coking oven straight chainhydrocarbons, such as paraflin hydrocarbons occurring in petroleum andthe like, to convert them into aromatic hydrocarbons, such as benzol,toluol, xylol, naphthalene, anthracene, and the like, while evolvingvapors containing straight chain hydrocarbons from a fluid hydrocarbonmass and carbonizlng the residue thereof into coke, and to the improvedand novel apill paratus or coke oven combination for carrying theaforesaid methods into practice.

Heretofore, various methods have been used for converting hydrocarbonsinto other hydrocarbon reaction products. Generally speaking,- suchconversions were formerly conducted in a variety of apparatus, includingstills, cracking units, etc. In recent years, attempts have been made toconduct the pyrolytic conversion of petroleum hydrocarbons in ovens,such as coking ovens of the broad type. Various difficulties wereencountered in these attempts and unsuccessful. results orunsatisfactory results were obtained, including failures in certaininstances. The most serious difficulties encountered were the choking upof channels and conduits with carbon, carbon residues, soot, and thelike, the production of low yields of aromatic hydrocarbons, the poorcoking of the residue of fluid hydrocarbon masses, and the poor qualityand low grade of the aromatic hydrocarbons and coke which were produced.In attempts at actual commercial operations of the pyrolytic conversionof hydrocarbons, the results obtained were so poor that the operationswere discontinued and were given up as commercially inadvisable or asindustrial failures. overcome the foregoing difliculties, none, as faras I am aware, has been wholly satisfactory for commercial operationconducted on a full industrial scale.

The present invention involves the discovery that in crackinghydrocarbon vapors evolved during the cokin of petroleum residue, forinstance, for the production of aromatic hydrocarbons, it is necessaryto control not only the direction of flow of the vapors and thetemperature of the cracking fluids, but also the space velocity and theturbulence of the vapors. It has likewise been discovered that acracking oven having a Although various endeavors were made to 2 specialstructure must be provided in order to properly carry out the pyrolyticconversion of hydrocarbons while at the same time heating fluidhydrocarbon masses to evolve hydrocarbon vapors and to carbonize theresidue into good coke having acceptable qualities and properties.

It is an object of the present invention to provide for the pyrolyticconversion on a commercial or industrial scale of low cost hydrocarbonresidual oils or the like to provide light oils, benzol, toluol, xyloland other aromatic hydrocarbons, together with coke, of a high qualityand high yield.

It is another object of the invention to provide an improved process forthe cracking of straight chain hydrocarbons and their conversion intoaromatic hydrocarbons with a sufficiently high yield to warrantindustrial operation.

A further object of the invention is to provide a new and improvedcombination of a coking oven and cracking chamber in which refractorymaterials are employed within a single structure capable of heating afluid hydrocarbon mass to evolve hydrocarbon vapors therefrom and tocarbonize the resulting residue therefrom into coke, thereby effectingthe pyrolytic treatment of the evolved vapors containing straight chainhydrocarbons and their conversion into aromatic hydrocarbons.

'It is also within the contemplation of the invention to provide a newand improved broad sole fired coking oven in which tar and carbonresulting from the pyrolytic treatment of hydrocarbons can be made intoa high carbon coke having a true specific gravity of 2 or more, andsuitable for the manufacture of carbon electrodes.

It is still a further object of the invention to provide a cracking andcoking oven of novel and improved design providing a heating system forthe distillation of heavy petroleum tar or the like and also a separateheating system within the same oven structure for the crackingof the oilvapors and the pyrolysis of parallins for the production of aromaticoils and other aromatic hydrocarbons.

It is also an object of the invention to provide an improved broadcracking and coking oven having the walls of the vapor flues constructedwith uneven surfaces to produce turbulence of the oil vapors in such amanner as to cause the oil vapors to contact the hot wall surfaces,whereby efiective pyrolytic treatment of hydrocarbons can be conducted.

Moreover, it is an object of the invention to provide a cracking andcoking oven involving novel and improved combinations in which anincreased.

and positive control of the flow and velocityof the oil vapors throughthe vapor flues is maintained, and in which positive control of the airto be preheated is provided, together with positive control of the wastegas from the oven, the said combinations involving an arrangement ofstructural elements which are capable of causing the air being heated toflow through horizontallydisposed recuperator tubes and of causing thewaste gas which is being cooled to flow around the recuperator tubes,whereby uniformity offlow and an effective change of temperature isimparted to the air from the sensible heat in the waste ases. gFurthermore, it is an object of the invention to provide a broadcracking and coking oven having a multiplicity of straight, independentheating flues extending parallel to the oven and divided on the centerline of the oven, so that the heating flues connect on each side of thecenter line of the oven with two separate recuperators, thus providingfor a continuous stream of the heating gases throughout the wholeheating system from each flue burner to the recuperators and the stack.

The invention likewise contemplates the provision of an ovenstructure'in which flues are employed below each floor heating flue forthe recirculation of the waste hot gases from each heating flue, for thepurpose of providing more uniform heating of the oven floor by extendingthe flame length by means of the recirculated waste gases.

It is still another object of the invention to provide a structure inwhich the recirculation of the waste gases passing through and aroundthe flames from the floor burners reduces the flametemperature due tothe presence of water vapor in the waste gas. It is a further object ofthe invention to provide a broad sole flred oven having a multiplicityof burners and heating flues under constant and uniform temperaturewithout having to reverse taken on the section line 3-3 of Fig. 1, inwhich the flow of air is indicated through the tubular recuperators bymeans of arrows, and the flow of oil or other hydrocarbon vaporsdirectly from the oven to the vapor off-take is also indicated by meansof arrows:

Fig. 4 is a vertical cross-sectional view taken on the section line 44of Fig. 1, in which the travel of the waste gases from the lower heatingsystem into the recuperator is indicated;

Fig. 5 shows an end view of the even from the right in Fig. 1, takenfrom the section line 5-5, showing the gas and air piping to the lowerand upper heating system, and air pipe connections to the vapor crackingflues;

Fig. 6 is a horizontal sectional view of the recuperators taken on thesection line 6-6 of Fig. 1, in which the flow of waste gas and incomingair is indicated by arrows;

Fig. 7 depicts a horizontal sectional view taken on the ection line 1-1of Fig. 1, in which the flow of waste gas into the recuperators isindicated by arrows;

Fig, 8 is a horizontal sectional view taken on the section line 8 8 ofFig. 1, showing the flues connecting the air flues from the recuperatorswith the lower heating flues;

Fig. 9 illustrates a horizontal sectional view taken on the section line9-9 of Fig. 1, showing the waste gas recirculation flues, in which theflow of the waste gas to the preheated air flues is indicated by arrows;

Fig. 10 is a horizontal sectional view taken on the section line I 0lllof Fig. 1 directly below the floor of the oven and showing the lowerheating flues;

Fig. 11 depicts a horizontal sectional view taken on the section line"-4! of Fig. 1, showing the longitudinal flues of the upper heatingsystem dithe flow of the waste gases, through structural means forpreheating the air. Still another object Of the invention is to providean improved oven construction for the production of coke and thecracking of hydrocarbon oils, in which cracking flues are so locatedthat a separate long heating flue is directly below and parallel to eachindividual cracking flue, and in which each oil vapor cracking flue issupplied with an air jet for the purpose of burning out any carbon whichmight collect in each oil vapor flue.

With these and other objects in view, the invention comprises thevarious features and combinations hereinafter more fully described andmore particularly defined in the annexed claims. I

The invention is illustrated in and described in connection with theaccompanying drawings, in which:

Fig. 1 is a vertical longitudinal sectional view showing a coking oven,tubular recuperators, upper heating flues, lower heating flues. wastegas recirculation flues and other flues in which the oil or otherhydrocarbon vapors are cracked, gas manifolds, and piping to the upperand lower longitudinal heating systems, waste gas outlets and crackedoil vapor oil-takes.

Fig. 2 illustrates a vertical cross-sectional view of an oven showingthe vertical recuperators' lower heating system, waste gas recirculationflues, upper heating flues. flues in which the oil vapors are cracked,the air supply to the recuperators, and the air and oilports leadinginto the oven;

Fig. 3 depicts a vertical cross-sectional view rectly below the floor ofthe oil vapor cracking flues;

Fig. 12 shows a horizontal sectional view taken on the section linel2-l2 of Fig. 1, showing the.

oil vapor cracking flues extending longitudinally of the oven, the viewshowing in detail the irregular surfaces of the cracking flues; and aFig. 13 illustrates a diagrammatic perspective view of my novel ovenclearly showing the flow of gas, air, fuel, steam, oil or tar, etc.,therein.

Broadly stated, the present invention contemplates the pyrolyticconversion of hydrocarbons for the production of aromatic hydrocarbons,such as benzol, toluol, xylol and the like, by the heat treatment ofpetroleum residues or other hydrocarbon oils. tars, or materials toproduce hydrocarbon vapors or gases in the manner hereinafter more fullyset forth. In accordance with themvention an apparatus is providedincluding an oven structure and cracking chambers or flues in which thepyrolytic conversion can be controlled within a temperature range toeffect the desired conversion.

By controlling the direction of flow of the hy-' ducted within a singlestructure having a novel I Y combination of cooperating elements bywhich improved results are obtained, eliminating certain operatingdifficulties of prior operations and substantially reducing the cost ofmanufacture of the products obtained thereby. Ahigh yield of aromatichydrocarbons and the production of electrode coke can be obtained by theprocessing of 8% degree API residuum oil, for example, by charging theoil into the oven at 700 F. and cracking the hydrocarbon vapors producedtherefrom at a temperature of about 1350 F., for instance, in thecracking chamber, or cracking flues,

hereinafter described and the sub-sequent recovery and separation ofcomponents of the reaction produced.

The single novel structure or apparatus employed in carrying out thepyrolytic conversion of the hydrocarbons includes a broad cracking andcoking oven which, in a commercial installation can be about 42 feetlong and about 10)/{ preheated air from-recuperators-and mixed withrecirculated hot waste gases. Housed Within the upper part of the ovenstructure'is a cracking chamber provided withan independent heatingsystem which can be so controlled as to obtain the desired temperaturein the floor and side walls of the oil cracking fiues, The entire brickwork'structure is preferably encased in a metal shell, such as a weldedsteel casing, whereby the interior of the oven may be operated underpressure or under sub-atmospheric. pressure, as desired.

Generally speaking, the .-oven heating system below theovenifloorpreferably consistsof any suitable number of fines, dependingupon the oven width employed, the fluesbeing preferably arrangedlongitudinally of the oven tosupport and heat the floor thereof. "Eachlongitudinal flue is preferably divided at its transverse center line sothat the waste gas-from each half flue is diverted into the recuperatorssituated below and parallel to the corresponding half. of the oven. Thetwo the floor heating dues and to constantly receive,

the hot waste products of combustion which, in turn, pass to the ovenwaste-gas stack.

Referring more in detail to the drawings, it Will be understood that thecracking and coking oven embodying my invention comprises an archedrectangular broad coking chamber O| in which the fluid hydrocarbon mass,such as oil residue, tar or the like, is heat treated and distilled,leaving carbon, which is one of the products of the reaction or heattreatment, on the oven floor to be coked. ber are flues VF-l, in whichvapors from the mass of fluid hydrocarbons are heat treated. The hot oilor tar is charged into the coking chamber 0-! through charging ports Piin both sides of the side Walls of the oven. The oil vapors pass fromthe coking chamber O-| through damper-controlled off-take ducts D, atboth sides of the oven, into a top plenum chamber P-2, and thencethrough ducts D-l, controlled by dampers D-l, into vapor heat-treatingflues VFI and Superimposed upon the coking chain 7 out of the ovenstructure through breaching 3-! and wash-oil valve V-2. into a. vaporflue V--3 to a conventional or standard by-product recove y apparatuswell known to those skilled in the art.

At the beginning of the distillation Process,-

dampers D4 (see Fig. 2) in both of the ducts D, the dampers D-3 (seeFig. 3) in both of the ducts D-2 being open, thus permitting the vaporsto flow directly to the breeching B-|, through the wash-oil valve V2,-to the vapor main V-3, and from thence to the by-product recoveryapparatus. After the floor of the oven is covered with the hydrocarbonoil or tar to be treated, and coking has started, dampers D4 in both ofthe ducts D may be opened, and the dampers D'-3 inboth of the ducts D-2can be closed. The flow or travel of ,the oil vapors then takes placethrough. the oil cracking vapor fiues VF--l to the breeching B-l,through the wash-oil valve V--2, to the vapor main V-3, and to theby-product recovery apparatus. During the entire oil cracking operation,the oven is sealed against the admission of air by means of ovendoorsOD-l, provided at the coke pusher end (see leftendin-Fig. 1) andalso at thecoke discharge end of the oven.

Beneath each half of the coking chamber 0-4 (see the left and righthalves, referring to Fig. 1) and-running parallel to the length thereofare heating flues 1,2, 3, 4, 5, 6, 1, Band 9 (see the left 'half 'ofFig. 1, and.Fig.- 3)'and l-F, 2'F, 3 F, ".4F, 5--F 61-h, and 9-1 (seethe right half of Fig. 1 and Fig. 2), which are preferably arrangedhorizontally, and each half flue is preferably independent of theadjoining fiues. The fiues are separated from .each other bylongitudinal partition walls as is indicated in Figs. 2 and.'3 of thedrawings. The heating flues I to 9 (Fig. 3) and l-F-to 9F (Fig. 2) areprovided at the outer ends thereof with suitable heat- (see Fig. 1),which can be supplied with fuel in a manner to be hereinafter described.Below each floor heating flue is a recirculation flue RC, for therecirculation of hot waste gases from and to each floor heating flue, soas to produce, during the operation of the apparatus, a long flame andto provide uniform heating of the oven floor.

Below the recirculation flues RC on each half of the oven are locatedtwo sets of recuperators Ri, R-2 and R-3, R-4, the recuperators R-l andR-2 being in series, and R-3 and R 4 beiug also in series, but the twosets in series operate independently of each other, as will be apparentfrom the detailed description of the operation of the apparatushereinafter more fully set forth. The tubes of the recuperators arepreferably constructed of silicon carbide, which permits the almostinstantaneous transfer of the sensible heat from the hot waste gasthrough the wall of the tubes to the air to be preheated.

The recuperator 13-3 is connected with the floor heating flues I to 9,inclusive, through ducts D-S (see Fig. 1), and the recuperator R| isconnected with the floor heating flues l--F to 9F, inclusive, throughducts D-6 (see Fig. 1).

The recuperators R-2 and R,-4- are connected with the waste gas flueC---! (see Fig. 1 and Fig.

It will be.understood that the portion of the apparatus heretoforedescribed in detail relates to the lower half of the oven unit, which isused primarily for the distillation of the hydrocarbon oil or tar andfor the coking of the residue. The upper portion of the apparatus isdesigned particularly for the treatment of oil vapors from thehydrocarbon oil or tar to effect cracking or the pyrolyticheat-treatment of the hydrocarbon vapors for the production of aromaticoils or compounds. The oven sections or parts are designed to'beoperated as a single unit, but the oil vapor" cracking flues VFI may beclosed ofi, if desired, by means of dampers D- l (see Fig. 2) and theoven maythen be operated solely as a distillation andcoking oven for theproduction of coke and high B. t. u. oil gas.

The heat-treating flues VF-l (see Figs. 1, 2, 4 and 12) which mayconsist of any desired number of flues, as may be required to handle thevolume and velocity of the oil vapors produced, are preferably arrangedhorizontally, or in a horizontal position longitudinally of the oven,and may be separated from each other by longitudinally arranged siliconcarbide partition walls W Gee Fig. 12), each of which has a multiplicityof projections T which serve to cause turbulence of the oil vaporsduring passage of the vapors in contact therewith and to produce moreintimate contact with the wall surfaces.

Each duct D-| is preferably provided with regulating dampers D-'l (seeFigs. 1 and 2) for the purpose of controlling the volume of oil vaporsfrom the plenum chamber P2 to each of the vapor cracking flues VF-- -l.Each vapor flue is preferably provided with an air inlet A-I from amanifold A for burning carbon in the cracking flues. Beneath, each vaporcracking flue, and arranged in. a horizontal position longitudinally ofv each vapor flue VF-l, is a heating flue CF--I (-see Figs. 1, 2 and1-1). These heating flues CF| ar preferably single and are separated bypartition walls W-l, as shown in Fig. 11. Each heating flue ispreferably provided with a separate gas or oil .burner 3-4, which may besupplied with gas or oil from a manifold B. The products of combustionfrom all of the heating flues CF| discharge into a flue -4 (see Figs. 1and 11) and through a stack flue C3 to a Waste-heat boiler, or to theatmosphere as desired.

When hydrocarbon vapors from the charge of residue oil or tar have beenevolved and there are substantially no more vapors to heat-treat in theflues VF-l, and the carbonaceous residue has been thoroughly coked, thenthe cok product is ready to be pushed from the oven into a standardquenching car or other suitable container.

The circulation of gases through the apparatus is as follows:

Hot waste gas from the floor heating flues I to 9 inclusive at the leftside of the oven in Fig. l, flows through ducts D-5, then 'around thesilicon carbide tubes SQ in the recuperator R3, then around the tubes SCin the recuperator R-4 and into the stack flue Cl. Simultaneously, hotwaste gas from the heating flues F-I to F-B, inclusive, at the rightside of the oven in Fig. 1,- flows through the ducts D-G into therecuperator R-I, around the silicon carbide tubes SC therein, thenthrough the passageway at th right into the recuperator R2 around thesillcon carblide tubes therein and then into the stack flue C-- The airrequired for combustion in the floor heating flues enters the apparatusthrough the duct A2 (se Fig. 2) and passes through duct D-8, from whichit is distributed through the silicon carbide tubes SC in therecuperator R-I, where it is preheated, and then passes into the duct orpassageway D9 and is distributed therefrom into the silicon carbidetubes SC oi the recuperator R-l, where the temperature is normallyraised to about 1500 F. The air then passes from the tubes in therecuperator R-l into the duct D-l0, from which it passes into duct D-H(see Figs. 2 and 8) and fromthence to ducts D-l2, then upward throughducts D-l3, then upward through the lateral ducts or passageways Dl4(see Fig. 1) into the heating flues i to 9 inclusive, and l-F to 9-Finclusive, under the oven floor.

The volume of preheated air to each floor heating flue may be regulatedas desired by means 'of dampers D-IS (see Fig. 1), the air serving tosupport combustion of the oil Or gas burned by the burners 13-2 at theright end of the oven in Fig. 1, and B'3 at the left end of the oven, asshown in Fig. 1. Each of the burners B-2 and B3 is operated underpressure and has an inspirator action, which not only causes forwardflow of the preheated air, but also draws a large volume of hot wastegasfrom each floor heating flue through openings or ducts CF-2 (see Fig. 1)into the recirculation flue RC and causes the hot Waste products to mixwith theair in the duct D-'-l4 (see Figs. 1 and 9) directly below eachburner 3-2 and B3. At the inner end of the recirculation flues areprojections PF (see Fig. 1)

which extend upwardly into each heating flue and serve to deflect avolume of the hot waste gas into each recirculating flue RC.

The improved method embodying the present invention may be carried outin any appropriate oven. For instance, a structure similar to thatdescribed and illustrated in my co-pending application Serial No.510,760 may be used, but the novel system herein described, having oilvapor cracking flues located directly above separate heating flueslongitudinally of the vapor flues and the oven, has demonstrated thevalue of the improved method in actual practice in the crack- 'to about700 F. and is then continuously sprayed into the coking chamber atvarious points through ports Pl. The oil rapidly covers the entire ovenfloor or the carbonized residue thereon, and vaporization of the hot oilbegins substantially immediately, together with the carbonizing of theresidue and the pyrolytic treatment of the oil vapors proceeds, asdescribed,

The process can be advantageously conducted using an eight houroperating cycle divided substantially as follows: The oven can bemaintained on stream, that is, with oil being continuously fed into theoven, during a period of about flve and one-half hours; the timerequiredfor coking is about seven hours, including the time that the oven is onstream; and the time required for pushing the coke from the oven and forlutinB or sealing the oven doors and burning the deposited carbon in thecracking fines is about thirty minutes, thus requiring substantiallyeight hours to complete the cycle. The carbon which is deposited overthe surfaces of the vapor cracking fiues during the cracking operationis quite flufly and is readily burned off by blowing air into each vaporcracking flue through pipes A-| (see Figs. 1 and 5) during the lastthirty minutes of operation of the cycle. The coke which is produced hasa true specific gravity, as distinguished from the apparent specificgravity, of about 2.0, or more, and may contain from upwards of about 90to about 98% or so of fixed carbon, together with a small amount ofvolatile matter, and up toabout 0.5% of ash. The following specificationhas been satisfied by my coke: 4

Maximum percentage Moisture 0.0 Volatile matter 0.5 Ash 0.45 Silicon0.06 Iron 0.06 Calcium 0.00 Sulphur 0.40 Soluble salts 0.05 Carbon 98.48

Total 100.00

Real density or true specific gravity minimum 2.00

In the coking of any carbonaceous material, a

certain percentageof fine or small particles of coke, known as breeze,is produced. This breeze is mixed with the petroleum residue referred tohereinbefore and is coked as previously described. The product can besold as electrode coke or as a fuel.

The control of the floor temperature of the oven is necessary in orderto satisfactorily regulate the steps of the process from the point atwhich the oil, tar, or the like is sprayed over the oven floor surface.In order to maintain control of the oven floor temperature, the gas tothe burners in the heating flues l to 9, and l--F to 9F, under the floorof the. oven is reduced in volume so as to reduce the temperatur of thefloor from about 2,000 F. to about 1,350 F. The tempera- 10 a -F.. andthat contact of the oil vapors with the hot surfaces of the crackingflues VF-l is required in order to bring about the conversion ofstraight chain hydrocarbons into aromatic hydrocarbons. To insurecontact of the hot hydrocarbon vapors with the hot cracking andheattreating surfaces of the cracking flues, means are provided on thesurfaces thereof for causing turbulence of the hot oil vapors. Toprovide for an average temperature of about 1350 F. within the crackingflues VF-I, the floor and side walls of each of the'vapor fiues arepreferably constructed of silicon carbide in order to attain almostinstantaneous transfer of heat to the oil vapors, and to maintain therequired uniform temperature of the vapor contacting surfaces. It hasbeen found as a result of experiments and tests that it is necessary tocause the hydrocarbon vapors to intimately contact the hot surfaces ofthe oil cracking flues in order toeffect the conversion of straightchain hydrocarbons into the desired aromatic hydrocarbons, The upperheating system heretofore described, including the superimposed vaporcracking lines. has been designedly incorporated in connection with theoven structure of my invention as a means of heating each vapor crackingflue by means of heat radiated into each vapor cracking flue. By means 1of the structure as shown and described, turbuture of the oven floordrops rapidly as the volume of fuel gas' is reduced, and as the oilcovers the floor of the oven, the volume of fuel gas to the heatingflues is increased. Furthermore, as the depth of the coke over the floorof the oven in creases, more gas is used at the burners to raise thetemperature as required for coking the incoming oil which is beingdeposited, until at the end of the oil input, when the coke bed is aboutseven inches thick on the average, then the temperature in the heatingflues is raised to an average of about 2750 F. which is necessary tocomplete the coking of the oil carbon residue on the top surface of thecoke.

Referring now more particularly to the production of aromatichydrocarbons from the straight chain hydrocarbons evolved in the ovenduring the distillation process, it has been found in actual practice ina broad oven of my invention that the exothermic reaction temperaturerelating to the conversion of straight chain hydrocarbons to aromatichydrocarbons will average about 1350 lence of the oil vapors in passingthrough the oil vapor cracking flues is produced, resulting in theintimate contact of the oil vapors with the hot wall surfaces.

The present invention provides a new design of a cracking and cokingoven, which in actual practice can be from about thirty to forty feetlong at the inside, between the oven doors OD-l about 10% feet in width,from the pusher end door to the discharge end side of the oven, andabout 2 feet in height at the spring line of the arch over the cokingchamber and about 4 feet 8 inches in height under the arch at the centerof the oven. The heating fines of the cracking chamber preferably have afree cross-sectional area of about square inches. It will be understoodthat although the cracking chamber VF-l is heated in part from the heatcoming from the oven Ol, the independent heating flues CF--l provide theadditional heat required for the cracking and heat-treating of thehydrocarbon vapors. Each separate heating flue is also preferablyprovided with a means of control for the amount of fuel to be burned bymeans of the burners 3-4, and thus of the amount of heat evolved forradiation and conduction to the vapors in the vapor cracking flues VF-l.

In carrying the process into practice, the temperature of the floor andwalls of the cracking lines are preferably maintained at about 1800" F.,thus providing a cracking flue temperature of about 1350 F. for theconversion of straight chain hydrocarbons to aromatic hydrocarbons, suchas light oils, from which benzol, toluol, and xylol can be obtained.

For the purpose of evolving hydrocarbon vapors from the oil residues,tar, and the like, in the oven O- l, a controlled amount of heat issupplied by the heating flue system under the oven floor and any desirednumber of heating fiues may be employed as may be required in any giveninstallation.

The theory underlying the pyrolysis of hydrocarbons is not completelyunderstood at the present time and the mechanism of the chemicalreactions involved is very complex. In the converthose of theendothermic type as well as those of the exothermic type. Generalyspeaking, the decomposition of hydrocarbons belongs to the endothermictype, whereas those relatingto poly- 'merization belong to theexothermic type. In the conversion of straight chain hydrocarbons toaromatic hydrocarbons it appears that the flrst reactions are of thedecomposition variety and are subsequently followed by those of apolymerizing'variety which may also be accompanied with various sidereactions. Although many factors are involved, it appears that the moreimportant are temperature,. time or space velocity, turbulence of thevapors, pressure, concentration, and contacting surfaces, Under certainconditions, including the use of appropriate catalysts, such products asbutadiene and other hydrocarbons may be formed. By controllingthe-conditions in the cracking and heat treating chamber a variety ofproducts can be produced. It is understood, however, that the presentinvention is not to be restricted to and dependent upon any theoryincluding the foregoing.

Although the present invention has been disclosed in connection with'apreferred embodiment thereof, variations and modifications may beresorted to by those skilled in the art without departing from the truespirit and scope of the invention as disclosed in the foregoingspecification and defined by the appended claims. Thus, for instance,the present method, and the coking and cracking oven above described,may be used for coking and the distillation of coal tar and coal tarpitches, for the recovery of a variety of compounds including creosoteand tar acids, and for the recovery ofvolatile products includingvolatile oils. Moreover, the novel process and oven heretofore describedmay be used for heating of oil shales and for the recovery of variousby-products including oil and fractions thereof.

Having thus described the invention, what claimed as new is:

1. A cracking and coking oven for the pyrolytic treatment of hydrocarbonmaterial to produce aromatic hydrocarbons and coke therefrom, whichcomprises a, longitudinally-extending main coking chamber, a series ofheating fiues directly below the floor of said chamber arranged side byside on each half of the chamber, means for heating each of said heatingfiues, a recirculation flue below each of said heating fiues andcommunicating therewith at the end portions thereof, a recuperator setbelow each longitudinal half of said main coking chamber, saidrecuperator sets having hollow heat-transmitting tubes therein adaptedfor the passage of air therethrough, said tubes extending transverselyto the longitudinal direction of said main chamber, a passagewayextending from said heating fiues through the recuperator sets aroundsaid tubes to a waste-gas discharge flue, means for passing air throughsaid tubes into said heating fiues so as to preheat the air passingthereto, a series of cracking fiues above said longitudinallyextendingmain cokingchamber, a passageway for oil vapors from said main chamberinto said above said main coking chamber and immediately below saidcracking fiues for heating said cracking fiues, means for dischargingcracked hydrocarbon vapors from said cracking fiues,

means for condensing a portion of said vapors,

and means for recovering the uncondensed portion of the vapors.

2. A refractory cracking and coking oven of the broad rectangular typefor the pyrolytic treatment of hydrocarbon oils to produce aromatichydrocarbons and coke therefrom, which comprises alongitudinally-extending main refractory coking chamber having a widthgreater than its depth, refractory chamber heating fiues directly belowthe floor of said coking chamber on each longitudinal half thereofextending longitudinally of the chamber, means for heating each of saidheating fiues, a refractory recirculation 5 flue below each of saidheating fiues and communicating therewith at the end portions thereof, arefractory recuperator, set below each longitudinal half of the. saidlongitudinally-extending main chamber, said'recuperator sets havinghollow heat-transmitting tubes therein and extendrefractory roof of saidlongitudinally-extending.

main coking chamber, each of said cracking fiues extendinglongitudinally of said coking chamber for substantially its entirelength, means for, passing a hydrocarbon oil into the main coking Ichamber, a passageway for oil vapors from the series of cracking fiues,a series ofheating fiues said main chamber into the said series ofrefractory cracking fiues, means independent of the chamber heatingfiues for maintaining the temperature underneath the cracking fiues suchas to produce aromatic hydrocarbons from the hydrocarbon vapors passingthereto during the porcarbon vapors are produced, means for dischargingthe hydrocarbon vapor product from said cracking fiues, means forcondensing a portion of the said discharged vapor product, means forcollecting the uncondensed portion thereof, means for discontinuing theflow of hydrocarbon oil to said main coking chamber to arrest thevaporgenerating portion of the pyrolytic treatment and means for passingair into the said cracking fiuesafter the vapor-generating portion ofthe treatment is arrested so as to burn on collected carbon in the saidcracking ues.

3. A cracking and coking oven for the pyrolytic treatment of hydrocarbonoils to produce aromatic hydrocarbons and coke therefrom which comprisesa longitudinally-extending main coking chamber, means for passing ahydrocarbon oil to be pyrolytically treated into said main cokingchamber during the oil vaporizing portion of said treatment, heatingfiues directly below the floor of said chamber on each longitudinal halfthereof, means for heating each of said heating fiues to provide acoking temperature during the coke forming portion of said treatment, arecirculation flue below each of said heating flues'communicating'therewith at the end portions thereof, a recuperator set below eachlongitudinal half of the said longitudinally-extending main chamber,

said recuperator sets having hollow heat-transmitting tubes thereinextending transversely tion of the pyrolytic treatment in whichhydrorecuperator set into said heating flues so as to preheat the airpassing thereto, a series of cracking flues above saidlongitudinally-extending main coking chamber, said cracking flues havingpartition walls of uneven surfaces at the interior of the flues to causeturbulence of the oil vapors passing therethrough in contacting with theuneven surfaces, a passageway for oil vapors from said main chamber intosaid series of cracking flues, a series of cracking flues heating fluesabove said main coking chamber for independently heating said crackingflues, means for passing hot products of combustion through saidcrackingflue heating flues to control the temperature of said crackingflues during the oil vaporizing portion of said treatment, means fordrawing off cracked hydrocarbon vapors from said cracking flues whilethe temperature thereof is maintained within temperature limits toproduce substantial proportions of aromatic hydrocarbons during saidcoke-forming portion of said treatment, means for condensing acondensible. portion of said cracked hydrocarbon vapors, means forcollecting the uncondensed portion of said vapors, means for removingcoke from said main coking chamber and means for passing air into saidcracking flues to burn collected carbon therein during the remainingportion of said treatment.-

4. A cracking and coking oven for the pyrolitic treatment of hydrocarbonoils to produce aromatic hydrocarbons and coke therefrom which comprisesa longitudinally-extending main coking chamber, means for passing ahydrocarbon oil to be pyrolytically treated into the said chamber duringa portion of said treatment, heating flues directly below the floorofsaid chamber on each longitudinal half thereof, means for heating eachof said heating flues to provide a temperature on the floor of saidchamber sufiicient for the production of coke from said hydrocarbon oiland to vaporize the uncoked portion of said hydrocarbon oil, arecirculation flue below each of said heating flues communicatingtherewith, at the end portions thereof, a recuperator set below eachlongi-' tudinal half of said longitudinally-extending main chamber, saidrecuperator sets having hollow silicon carbide tubes therein extendingtransversely therethrough, a passageway extending from the heating flueson each longitudinal half of said main chamber through the adjacent rea!cuperator sets around said tubes therein to a waste-gas discharge flue,means for passing air into and through said tubes of the recuperatorsets to preheat the air passing into said heating flues, damper meansfor independently controlling the passage of air through said tubes inthe recuperator sets on each longitudinal half of said main chamber, aseries of cracking flues above said longitudinally-extending main cokingchamber extending longitudinally thereof, said cracking flues havingprojections on the interior walls thereof to cause turbulence of oilvapors passing therethrough and to provide intimate contact thereof withsaid projections to produce rapid heat transfer to said vapors, apassageway for oil vapors from the said main chamber into said series ofcracking flues, means for controlling the volume of vapors through saidpassageway to each of said cracking fiues, a series of cracking-flueheating flues above said main coking chamber and immediately below saidcracking flues for heating the same, means for passing hot productsofcombustion through said cracking-flue heating flues to provide atemperature therein within a range sufficient for the production ofaromatic hydrocarbons from said oil vapors, means for discharginghydrocarbon vapors from the said cracking flues, means for controllingthe pressure within said main chamber and said cracking flues duringsaid pyrolytic treatment so as to provide for maximum production ofaromatic hydrocarbons at the temperature of operation within saidcracking flues, means for condensing a condensible portion of saidhydrocarbon vapors, means for collecting the uncondensed portion of saidhydrocarbon vapors and means for passing into said cracking flues toburn collected carbon therein during a portion of the cycle after thepyrolytic treatment of said hydrocarbon oils.

5. In a refractory cracking and coking oven of the broad rectangulartype-for the pyrolysis of hydrocarbons including the conversion ofstraight chain hydrocarbons into aromatic hydrocarbons containing only asmall amount of paraffins and containing only a small amount ofparaflins, an

off-take duct" connecting said oven with said cracking flue forconducting gases and vapors from said oven to said flue, refractoryheating flues independent of said oven heating flues and located in theroof of said coking oven and directly underneath said cracking flues tofurnish independent heat thereto, and means to control said independentheat to regulate the temperature of said cracking flues to effect amaximum conversion of said straight chain hydrocarbons into aromatichydrocarbons containing only a small amount of parafiins.

6. In a refractory cracking and coking oven of the broad rectangulartype for the pyrolysis of hydrocarbons including the conversion ofstraight chain hydrocarbons into aromatic hydrocarbons containing only asmall amount of paraflins and the production of coke having a density ofat least 2.0, thatimprovement which comprises a series of refractoryheating fiues directly below the floor of the coking oven, a series ofrefractory recirculation flues below said heating flues andcommunicating therewith at the end portions of the recirculation flues,means for passing a hydrocarbon oil into the coking oven, an elongatedrefractory cracking flue incorporated in the roof above said oven andhaving an extended passage therethrough for the conversion of straightchain hydrocarbons intoaromatic hydrocarbons containing only a smallamount of parafiins, means for regulating the temperature of the floorof the coking oven so as to control the coking of said hydrocarbon oil,an refractory off-take duct connecting said oven with said cracking fluefor conducting gases and vapors from said oven to said flue, refractoryheating flues independent of said oven heating fiues and located in theroof of said coking oven and directly underneath said refractorycracking flues to furnish independent heat thereto, and means toindependently control the heating of said latter heating flues toregulate the temperature of said cracking flues to effect a maximumconversion of said straight chain hy- Y of refractory recirculationflues positioned below said heating flues so asto communicate therewithat the end portions of the,recirculation flues, means for spraying ahydrocarbon oil onto the floor of said coking chamber, an elongatedcracking flue, incorporated in the roof above the said oven, havingwalls of refractory material with uneven surfaces therein and having anextended passage therethrough for the conversion of straight chainhydrocarbons into aromatic hydro carbons containing only a small amountof paraffins, means for regulating the temperature of the floor of thecoking oven so as to control the coking of said hydrocarbon oil, arefractory ofitake duct connecting said ovenwith said cracking flue forconductinggases an vapors from said oven to said flue, auxiliaryrefractory heating flues independent of said main oven heating flues'andlocated in the roof of said coking oven and directly underneath saidcracking flues to furnish heat'thereto and means to control saidindependent heat to regulate the temperature of 1 o. 1300 F. to 1800" F.in said cracking flues to ef-. fect a maximum conversion of saidstraight chain hydrocarbons into aromatic hydrocarbons containing only asmall amount of paraflins.

9. A refractory cracking and coking oven for the combined pyrolytictreatment of fluid hydrocarbon masses including residual petroleum oil,tar and the like, to convert straight chain hydrocarbons into aromatichydrocarbons including benzol, toluol, xylol and the like containingasmall amount of paraiflns, and the carbonization of the residue intocoke of high density, which comprises an elongated broad refractorycoking oven having a length greater than its width and a height lessthan its width, a main heating flue system located directly underneathand associated with said coking oven for effectively volatillzing vaporsof fluid hydrocarbon masses contained therein and for thoroughlycarbonizing residue from said hydrocarbonmasses into coke of highdensity, a recirculating flue operatively associated with said mainheating flue system to recirculate gases therein, a refractory vaporcracking flue system associated with the roof of said coking the heatingflues-and of said cracking flues to efiect a maximum conversion of saidstraight chain hydrocarbons into aromatic hydrocarbons containing only asmall amount of paraflins and the production of coke having a density ofat least 2.0, that improvement which comprises a series of separatedmain refractory heating fiues directly below the floor of said cokingoven on each longitudinal half thereof and a series of refractoryrecirculation flues positioned directly below said heating flues so asto communicate therewith at the end portions thereof, means for feedinga hydrocarbon oil onto the floor of said coking chamber, means forregulating the tempera ture of said floor during operation of the cokingchamber between about 1350 F. and 2,000 F., an elongated refractorycracking flue incorporated in the roof above-said oven, said crackingflue having walls of refractory material having a mul tiplicity ofprojections to cause turbulence of the oil vapors during passage of thevapors in contact therewith, said cracking flue having an extendedpassage therethrough for the conversion of straight chain hydrocarbonsinto aromatic hydrocarbons containing only a small amount of parafllns,a refractory ofl-take duct connecting said oven with said cracking fluefor conducting oven for I pyrolytically treating hydrocarbon vaporsvolatilized from said hydrocarbon masses and for converting said vaporsfrom'straight chain hydrocarbons into aromatic hydrocarbons includingbenzol, toluol, 'x'ylol and the like, containing a small amount ofparaffins, outlet means for removing said treated and converted vaporsfrom said cracking flue system and for conducting said vapors to aby-product recovery system, a controllable auxiliary heating flue systemmounted under said cracking flue system and capable of providing adesired and controlled cracking temperature in said cracking fluesystem, and a, recuperator system operatively connected to said mainheating flue system for effecting an exchange of heat-from said hotproducts of combustion going from said main heating flue system to astack to air coming from the atmos- Phere and going to said main heatingflue system to support combustion of fuel therein.

10. A refractory cracking and coking oven for the combined pyrolytictreatment of fluid hydrocarbon masses including residual petroleum oil,tar and the like, to convert straight chain hydrocarbons into aromatichydrocarbons including ,benzol, toluol, xylol and the like containing asmall amount of parafllns, and the carbonization of the residue intocoke of high density, which comprises an elongated broad refractorycoking oven having a length greater than its width and a height lessthan its width, an oven door mounted at each end of said coking chamberto seal the same from the atmosphere, a main heating flue system locateddirectly underneath and associated with said coking oven for effectivelyvolatilizing vapors of fluid hydrocarbon masses contained therein andfor thoroughly carbonizing residue from said hydrocarbon masses intocoke, a recirculating flue operatively associated with said main heatingflue system to re-circulate gases therein, a refractory vapor crackingflue system associated with the roofof said coking chamber forpyrolytically treating hydrocarbon vapors volatilized from saidhydrocarbon masses and for converting said vapors from straight chainhydrocarbons into aromatic hydrocarbons including benzol, toluol, xyloland the like, containing a small amount of parafflns, outlet means forremoving said treated and converted vapors from said cracking fluesystem and for conducting said vapors to a by-product recovery system, acontrollable auxiliary heating flue system mounted under said crackingflue system and capable of providing a desired and controlled crackingtemperature in said cracking flue system, and a recuperator systemoperatively connected to said main heating flue system for eflecting anexchange of heat from said hot products of combustion going from saidmain heating flue system to a stack to air coming from the atmosphereand going to said main heating flue system to support combustion of fueltherein.

11. A refractory cracking and coking oven for the combined pyrolytictreatment of fluid hydrocarbon massesincluding residual petroleum oil,tar and the like, to convert straight chain hydrocarbons into aromatichydrocarbons including benzol, toluol, xylol and the like, containing asmalfamount of paramns, and the carbonization of the residue into cokeof high density, which comprises an elongated broad refractory cokingoven having a length greater than its width and a height less than itswidth, a plurality of inlet pipes connected to and leading into theinterior of said coking oven for introducing fluidhydrocarbon massesincluding residual petroleum oil, tar and the like, a main heating fluesystem located directly underneath and associated with said cokingchamber for effectively volatilizing vapors of fluid hydrocarbon massescontained therein and for thoroughly carbonizing residue from saidhydrocarbon masses into coke of high density, a recirculating flueoperatively associated with said main heating flue system to recirculategases therein, a refractory vapor cracking flue system associatedwiththe roof of said coking chamber for pyrolytically treating hydrocarbonvapors volatilized from said hydrocarbon masses and for converting saidvapors from straight chain hydrocarbons into aromatic hydrocarbonsincluding benzol, toluol, xylol and the like, containing a small amountof parafllns, starting vapor outlets for removal or vapors at thecommencement of the operation of volatilizing vapors from said fluidhydrocarbon masses contained in said coking chamber, outlet means forremoving said treated and converted vapors from said cracking fluesystem and for conducting said vapors to a by-product recovery system, acontrollable auxiliary heating flue system mounted under said crackingflue system and capable of providing a desired and controlled crackingtem perature in said cracking flue system, and a recuperator systemoperatively connected to said main heating flue system for effecting anexchange of heat from said hot products of combustion going from saidmain heating flue system to a stack to air coming from the atmosphereand going to said main heating flue system to support combustion of fueltherein.

12. A cracking and coking oven for the combined pyrolytic treatment offluid hydrocarbon .masses including residual petroleum oil, tar and thelike, to convert straight chain hydrocarbons into aromatic hydrocarbonsincluding benzol, toluol, xylol and the like, and the carbonization ofthe residue into coke, which comprises an elongated broad coking chamberhaving a length greater than its width and a height less than its width,an oven door mounted at each end of said coking chamber to seal the samefrom the atmosphere, a plurality of inlet pipes connected to and leadinginto the interior of said coking chamher for introducing fluidhydrocarbon masses including residual petroleum oil, tar and the like, amain heating flue system associated with said coking chamber foreffectively volatilizing vapors 18 or fluid hydrocarbon masses containedtherein and for thoroughly carbonizing residue from said hydrocarbonmasses into coke, a recirculating flue opera'tively astociated with saidmain heati flue system to recirculate gases therein, a vapor crackingflue system associated with the root of said coking chamber forpyrolytically treating hydrocarbon vapors volatilized fromsaidhydrocarbon masses and for converting said vapors from straight chainhydrocarbons into aromatic hydrocarbons including benzol, toluol, xyloland the like, starting vapor outlets for removal of vapors at thecommencement of the operation of volatilizing vapors from said fluidhydrocarbon masses contained in said coking chamber, outlet means forremoving said-treated and converted vapors from said cracking fluesystem and for conducting said vapors to a by-product recovery system, agas main for the removal of vapors coming front said coking chamber andsaid cracking flue system, a controllable auxiliary heating flue systemmounted under said cracking flue system and capable of providing adesired and controlled cracking temperature in said cracking fluesystem, means to conduct hot waste gas from said auxiliary heating fluesystem to a pre-heater for preheating the fluid hydrocarbon massesincluding residual petroleum oil, tar and the like, prior to introducingthesame into said coking chamber, and a recuperatorsystem operativelyconnected to said main heating flue system for effecting an exchange ofheat from said hot products of combustion going from said main heat ingflue system to a stack to air coming from the atmosphere and going tosaid main heating flue system to support combustion of flue therein.

13. A refractory cracking and coking oven for the combined pyrolytictreatment of fluid-hydrocarbon masses including residual petroleum oil,tar and the like, to convert straight chain hydrocarbons into aromatichydrocarbons including benzol, toluol, xylol and the like, containing asmall amount of parafllns, and the carbonization of the residue intocoke of high density, which comprises an elongated broad refractorycoking oven having a length greater than its width and a height lessthan its width, means provided at each end of said coking chamber andcapable of sealing the same from the atmosphere and capable ofpermitting the removal of coke when said coking chamber is unsealed,means for introducing fluid hydrocarbon masses into said coking chamber,a main heating flue system located directly underneath and associatedwith said coking oven for efiectively volatilizing gases and vapors fromfluid hydrocarbon masses contained in said coking oven and forthoroughly carbonizing residue from said hydrocarbon masses into coke, arecirculating flue operatively associated with said main heating fluesystem to recirculate gases therein, an air inlet connected to theatmosphere to provide air for combustion of fuel in said main heatingflue system, a refractory vapor cracking flue system associated with theroof of said coking chamber for pyrolytically treating hydrocarbonvapors volatilized from said hydrocarbon masses and for converting saidvapors from straight chain hydrocarbons into aromatic hydrocarbonsincluding benzol, toluol, xylol and the like containing a relativelysmall amount of paraffins, off-take means connecting said coking ovenwith said cracking flue system for conducting gases and vapors from saidcoking oven to said cracking flue, a controllable auxiliary heatin fluesystem mounted under said cracking flue 19, system and capable ofproviding a desired and controlled crackifig temperature insaid crackingflue system, heat exchange means operatively connected to said mainheating flue system for efiecting an exchange of heat from hot productsof combustion going from said main heating flue system to a stack to aircoming from the atmosphere and going to said main heating flue system tosupport combustion of fluel therein, and outlet means for removing fromsaid cracking flue system treated vapors which have been converted fromstraight chain hydrocarbons into aromatic hydrocarbons including benzol,toluol, xylol and the'likeand containing a relatively small amount ofparafiins.

CHARLES H. HUGES,

20 REFERENCES CITED The following references are of record in the fileof this patent:

UNITED STATES PATENTS Number Name Date 1,885,920 Knowles et a1. Nov. 1,1932 1,907,029 Andrews et a1. May 2, 1933 2,116,641 Reppekus May 10,1938 2,234,173 Hughes I Mar. 11, 1941 2,259,380 Hughes II Oct. 14, 19412,267,447 Curran Dec. 23, 1941 2,347,076 I Boynton et a1. Apr. 18, 19442,199,841 Saleh May 7, 1940

